Embodiments of the invention relate to an apparatus, a method and a computer program for localizing a sound source. Some embodiments according to the invention relate to a rotating microphone field (also referred to as a microphone array) or rotating microphone fields. Some embodiments according to the invention relate to the construction of a rotating microphone field.
Some embodiments according to the invention relate to a Doppler microphone field or Doppler microphone fields.
In many cases, it is desirable to determine a position of a sound source or a direction from which sound comes or arrives. For example, there are systems in which it is desired to localize an object marked by a sound transmitter. Depending on the case of application, it may be desirable to detect only the direction in which the object is located, or even the exact position of the object. In the following, in general, the determination of complete or partial positional information (e.g. directional information) with regard to a sound source is understood by localization.
For localizing a sound source, there is a multiplicity of conventional concepts. For example, one or more linear microphone fields can be employed. When using one or more linear microphone fields, however, directional accuracy is limited by the length of the field. Hence, very long fields are necessary for exact location, for example. Moreover, accuracy of an individual measurement is limited, because the signal-to-noise ratio (SNR) is limited, for example. Furthermore, sometimes there is a problem regarding accuracy of the position or positions of the individual microphones in linear microphone fields. For a complete 3-dimensional measurement (3-D measurement), conventionally several fields are required in many cases. In some other conventional arrangements, rotation of a field or microphone field is necessary between the measurements, which may entail problems regarding accuracy and regarding the time needed.
In some further conventional concepts, a single microphone or a few microphones are moved between measurements by way of stepper motors. Positional accuracy is limited here in many cases by the length of a sampled or “scanned” area. For exact localization, very long fields are thus needed in some conventional arrangements. Furthermore, accuracy of an individual measurement is limited in some conventional arrangements, for example due to the limited signal-to-noise ratio.
When moving a single or a few microphones with stepper motors, the problem of the accuracy of the position of the microphone positions does not seldom arise. For example, problems may result due to tolerances of the stepper motor or due to vibrations of the construction. Furthermore, the construction of the arrangement for moving a single or a few microphones with stepper motors without reflections at fixtures is difficult.
Some further conventional arrangements include so-called circular fields (also referred to as “circular arrays”).
In some arrangements, using circular fields, directional accuracy is limited by the diameter of the field. In some conventional arrangements, very large fields are necessary for exact localization. Furthermore, the accuracy of the individual measurements is limited by the achievable signal-to-noise ratio, for example.
In some conventional arrangements, using circular fields, the problem of the accuracy of the position of the individual microphones arises. Furthermore, construction without reflections at fixtures is difficult in some cases.
In some further conventional arrangements, rotation of a single or a few microphones takes place in a circle with a stepper motor between measurements. Directional accuracy here is limited by a length of an area circumscribed in some cases. In some arrangements of such kind, a very large diameter is necessary for exact localization. Furthermore, accuracy of the individual measurements is also limited by an achievable signal-to-noise ratio (SNR), for example. In some arrangements there is also a problem with the accuracy of the position of the microphone positions. Problems regarding the accuracy of the position may, for example, result from tolerances of the stepper motor or from vibrations of the construction, particularly when using a long microphone arm.
In view of the above explanations, it can be seen that directional accuracy is limited by the size of the arrangements, in many conventional arrangements.
Hence, there is a need for a concept which enables, at given dimensions of an arrangement, obtaining particularly expressive information regarding the position of a sound source or regarding the direction from which sound arrives.